YZ125 second gear issue

[Patrick Ahern]

I just bought a 1997 yz125, lots of racing parts, bike runs AMAZING, starts first kick without choke. Only issue I have is I went out to ride today and when I shifted to second, I hear a clanking sound and can feel the bike trying to grab but it won't. I just replaced the clutch oil filled correctly with 10w-30 oil of the right grade, and the sprockets and chain are good. It's not the clutch because it rides perfect in all the other gears, 2nd is just garbage though. I know I have to split the case for this, but has anyone had any experience with an issue like this, or have any tips to share? I've found both gears on ebay for 2nd, and can get them both for under $100 combined, just don't want to pay $300 for my shop to split the engine. What specialty tools do I NEED, and what can I make do without? Thanks in advance!

[EmpireofDerp]

Bummer dude.

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[YZDOC]

Gears on ebay are a gamble as they are used also. If you can get new, get new. Second gear wheel and pinion, a couple C clips, and a manual to do it yourself. You will need a few tools to do it right, a full gasket set and seal kit, and main bearings. Might as well throw in a new top end when you get there, or ring (s) at least.

Edited August 2, 2017 by P84ONE

[Yzhabs]

There are johnnyshop videos on you tube. He shows step by step. Short and sweet. Really informative. Good luck

[Patrick Ahern]

Thanks, it does have a fresh top end on it already which is a plus. Do I have to worry about any of the other gears? I've never been inside a bike trans before so I'm not sure if it works in conjunction with another gear at all or not. If it's just going to be the second gear then that's awesome as I found both on ebay NOS for a decent price. How long do you think it would take me to do, as I've never done it before but I do have a fairly mechanical mindset and work with small engines and machines all the time. I'm 18 going to Penn State for Mechanical Engineering so this is the kind of stuff I like doing. 

1 hour ago, P84ONE said:

Gears on ebay are a gamble as they are used also. If you can get new, get new. Second gear wheel and pinion, a couple C clips, and a manual to do it yourself. You will need a few tools to do it right, a full gasket set and seal kit, and main bearings. Might as well throw in a new top end when you get there, or ring (s) at least.

 

[Patrick Ahern]

1 hour ago, john mcculloch said:

There are johnnyshop videos on you tube. He shows step by step. Short and sweet. Really informative. Good luck

I'll have to check them out, I'm looking online for a manual now as well

[YZDOC]

First time, take your time. So give it at least 10-24 hours of work, removing, striping, cleaning, inspecting, re-assemble. Watch the youtube videos, and we are all here to help you along. Transmissions are two gears for each gear, one on the main shaft and one on the output shaft, called a wheel and pinion gear respectively. There are C-clips that need to be removed (5 if I remember on a 125 also) and once removed, replace them. They have a sharp edge and a champhered edge, so remember sharp edge goes on outside force. Once you are inside and the case is split, it is good insurance to replace the main bearings, seals, and anything that looks like it has wear, especially the shift forks. Post photos, ask questions, and keep your thread alive with progress. 

[Patrick Ahern]

What manual should I go with, Clymer, Yamaha or Haynes? I've heard good things about Clymer but Yamaha seems like the better choice just by it being the factory manual.

[YZDOC]

Just now, Patrick Ahern said:

I'll have to check them out, I'm looking online for a manual now as well

try manualslib.com

[YZDOC]

https://www.manualslib.com/manual/196053/Yamaha-Yz125k1.html

Sorry, thats the parts cat. Hold on still looking

 

1998 should be close enough.

Edited August 2, 2017 by P84ONE

[Patrick Ahern]

Thank you so much! I'm planning on pulling the engine and getting a decent workspace cleared out in my mess of a shop tomorrow after work, so I'll update on my progress tomorrow night as I should have the issue diagnosed then. 

[rpt50]

The yamaha manual should have all the information you need.  An air impact gun will make removing the clutch hub and primary drive gear much easier.  I have never had much luck with those "clutch holding" tools.  The "Tusk" brand (Rockymountain) case splitter, FW puller, and crank puller tools have worked well for me.  Make sure you source the correct "yamabond" products (can't remember which numbers off the top of my head) before beginning.  Shops around here always seem to be out when you need it.  You will also likely need red loctite for internal parts.  And like the other guy said, the internal bearings of the transmission are pretty cheap.  Might as well replace them.  

I would also be prepared to replace some or all of the case bolts.  Given that they are 20 years old, they may be in pretty rough condition.

Unfortunately the tools you will need are not especially cheap, but since you are studying to be a mechanical engineer and will likely be doing your own bike work in the future, they are probably a good investment.  

[Smoking 2's]

I just did my yz 250 for this first, splitting cases installing crank etc. It seemed real scary at first but with all the help from p84one and motox367, it wasn't bad after all said and done. Look up 01 yz250 crank bearings from just a few weeks ago, I posted a bunch of pics and the reading also will be close to your job

Edited August 2, 2017 by Smoking 2's
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[Patrick Ahern]

Today's progress so far includes tearing down the frame and subframe and removing the engine. It's going pretty smooth so far and watching the johnnyshop video really helped, as he did the same bike in his videos, a complete tear down. Now that the engine is open, is it possible to get to the gear by just opening up the left side of the case, or do I have to remove the right side and the clutch as well? I'm working on getting assembly lube and the manual I need, then once I'm into the meat of her I'll get specific parts ordered.

[YZDOC]

You can leave it all in the right side if you like. Harder to clean up, but I have done it. But you are going to need to remove the transmission so it's pointless. GO DEEP, replace everything that looks questionable. 

[Smoking 2's]

As I was told, if your gonna do it, learn it all! P84ONE has your back that I assure. Rip it apart just don't force anything!!!!

[Patrick Ahern]

Went to the shop today and got lube and a manual, all he had was the Clymer but it seems to be pretty in depth and has everything in it I need, with pictures. Working on getting a few pullers and such from friends to use, then we'll be in!

[YZDOC]

What you got in your avatar, couple of 2-4lb bullhead cat? You must be in the midwest. When I lived on my dads farm for a year in in the 70's I used to fish for them, Channel, and Big Mouth Bass. Ate fish like three times a week, then there was always the fries of other body parts. Good times... 

 

[Kinger317]

You definitely want to inspect the dogs on the side of the gears, if they are rounded you'll need the gear next to it also. Maybe don't order anything until you get your eyes on everything.

[Patrick Ahern]

2 hours ago, P84ONE said:

What you got in your avatar, couple of 2-4lb bullhead cat? You must be in the midwest. When I lived on my dads farm for a year in in the 70's I used to fish for them, Channel, and Big Mouth Bass. Ate fish like three times a week, then there was always the fries of other body parts. Good times... 

 

They're channel cats, I caught them in the upper Chesapeake bay in Maryland. Fun to catch, I just use my bass rod for them and chuck out a shrimp on my line and wait. 

 

45 minutes ago, Kinger317 said:

You definitely want to inspect the dogs on the side of the gears, if they are rounded you'll need the gear next to it also. Maybe don't order anything until you get your eyes on everything.

That was my plan, I haven't ordered anything and don't plan on doing it until I have everything opened up. I've heard the term used plenty, but what exactly are the "dogs" on a gear?